1. Field of the Invention
This invention relates to a light measuring device for use in a photographic camera or a printer, is more particularly directed to a light measuring device capable of providing weighted brightness information in which the image area is divided into a plurality of sections that are differently weighted.
2. Description of the Prior Art
There have been known various kinds of light measuring system such as averaged light measuring, center-weighted measuring and partial measuring. In the averaged light measuring, the averaged value of the amount of light from the entire scene viewed by the taking lens of the camera is measured through use of a photodetector which has substantially the same angle of view as that of the taking lens. In this light measuring system, it is impossible to obtain a proper exposure of the photographic subject matter if there is a bright background behind the subject matter such as the sky or a back light. Though it is known to correct the exposure controlled by the averaged light measuring by use of a correction means which effects increase or decrease of the measured values, it is troublesome to operate such a correcting means and it is difficult to accurately correct the exposure to the optimum amount.
In the center-weighted measuring, the central part of an image is weighted in comparison with the marginal part. In the partial measuring, only a part of an image is measured. These two light measuring systems are based on an empirical rule that the subject matter of photography is normally located around the center of the scene aimed by a camera and weights the central part in comparison with the marginal part to reduce the weighting of the brightness information of the marginal part of a scene. Accordingly, these two light measuring systems are disadvantageous in that the exposure cannot be properly controlled based thereon if the subject mater is not located at or near the center of a scene if the difference in brightness between the central pat and the marginal part is too large.
Beside the above mentioned light measuring systems, there have been known in the art to use the maximum and minimum values of the brightness of some parts of a scene to obtain more practical information as disclosed in Japanese Unexamined Patent Publication Nos. 92622/1976, 13412/1978, 91224/1979 and Japanese Utility Model Publication No. 9271/1976, and to divide the scene into the upper half and the lower half to obtain information of these halves separately as disclosed in Japanese Unexamined Patent Publication Nos. 75442/1976, 96829/1978, 90926/1974, 90927/1974, 71834/1978, 118127/1978 and Japanese Patent Publication No. 8516/1971.
The above-mentioned various kinds of light measuring systems, however, are all disadvantageous in that it is very difficult to provide the optimum light measuring or the optimum image information for any kind of scene. In other words, the above systems are effective for a few particular kinds of scene but not for all kinds of scene, because the photodetectors and the measured value operating circuit are always the same for any kind of scene.